Centrifugal compressors are commonly used for fluid compression in rotating machines such as, for example, a gas turbine engine. Gas turbine engines typically include at least a compressor section, a combustor section, and a turbine section. In general, during operation, air is pressurized in the compressor section and is mixed with fuel and burned in the combustor section to generate hot combustion gases. The hot combustion gases flow through the turbine section, which extracts energy from the hot combustion gases to power the compressor section and other gas turbine engine loads.
A centrifugal compressor is a device in which a rotating rotor or impeller delivers air at relatively high velocity by the effect of centrifugal force on the gas within the impeller. A diffuser is commonly an annular space surrounding the periphery of the impeller and which usually is provided with vanes to guide the gas flow in order to recover static pressure and minimize turbulence and frictional losses in the diffuser. A diffuser is typically positioned downstream of the centrifugal compressor to de-swirl or align the air direction required for subsequent engine components. The air or other gas (which will be referred to hereafter as air) is delivered from the impeller with a velocity having a substantial radial component and, ordinarily, a substantially greater tangential component. The function of the diffuser is to decelerate the air smoothly and to recover as static pressure (head) the total or stagnation pressure (dynamic head) of the air due to its velocity.